Compact high voltage supply



Dec. 24, 1968 H Q 5|M0N ET AL 3,418,526

COMPACT HIGH VOLTAGE SUPPLY Filed May 15, 1966 6 Sheets-Sheet 1 GENERATOR H. C. SIMON 'ET AL COMPACT HIGH VOLTAGE SUPPLY Dec. 24, 1968 6 Sheets-Sheet 2 Filed May 13, 1966 Dec. 24, 1968 H. c. SIMON ET A1. 3,418,526

` COMPACT HIGH VOLTAGE SUPPLY Filed Ma'y 13, 196e e sheetssheet s 227 F IG. 4

FIG. IO

Dec. 24, 1968 H. c. slMoN ET Al- COMPACT HIGH VOLTAGE SUPPLY 6 Sheets-Sheet 4 Filed May 13, 1966 Dec. 24, 1968 H. c. SIMON ET AL COMPACT HIGH VOLTAGE SUPPLY 6 Sheets-Sheet 5 Filed May 15, 1966 Dec. 24, 1968 H. c. SIMON ET A|. 3,418,526

COMPACT HIGH VOLTAGE SUPPLY Filed May 13, 1966 6 Sheets-Sheet 6 43 |99130'P 203 El 29 |95 29| 243 "227 |9| 2? v T L.. IBI 45 -3 @l m |7| 305) 3 3 93297 2 F|G.|3.

GENERATOR United States Patent COMPACT HIGH VOLTAGE SUPPLY Harold C. Simon and Bernard V. Gerber, Baltimore, Md.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed May 13,1966,"Ser. No. 549,863 8 Claims. (Cl. 315-205) ABSTRACT OF DISCLOSURE A high voltage electrical supply comprising a plurality of split annular rings mounted concentrically about an axis and encased in a container filled with a gaseous dielectric material to permit a reduction in the gap between the high voltage terminal; ea'ch of the split rings comprising a plurality of series connected electrical elements arranged with the end terminals of the series connected elements adjacent the gap formed in the ring by the split thereof whereby the voltage gradients in the various split rings are a maximum across the gap thereof and a minimum along the surface thereof; one of the split rings being located concentrically within another of the split rings.

This invention relates to the power-supply art and has particular relationship to high-voltage power-supplies for energizing electron-beam generators for treating materials.

Typically such operations as precision welding and cutting and melting are currently being carried out with electron beams. While this invention has general applicability it isdescribed in this application as applied to electron-beam welding. Electron-beam welding apparatus includes an electron-beam generator which has a cathode, serving as a source of electrons and an accelerating anode in a highly evacuated chamber. A high accelerating potential of the order of 150,000 volts or more is impressed between the cathode and the anode to produce a sharp beam. The generator includes focusing facilities which focus the beam on or in the vicinity of work to be welded and deflectng facilities for moving the beam laterally of its axis.

This invention concerns itself with electron-beam welding apparatus for use with work outside of the vacuum chamber and it is an object of this invention to provide readily portable electron-beam welding apparatus.

In accordance with prior-art practices the electronbeam generator of an electron-beam Welder is powered from a xed high voltage supply. An electron-beam generator so powered is not readily portable because the supply itself is not portable and the connection of the highvoltage output terminals of the supply to the electronbeam generator requires a cable insulated for the high voltage which for movement over any reasonable distance is excessively heavy and cumbersome. It is an object of this invention to overcome this difficulty and to provide a portable electron-beam welder which shall include no heavy cable insulated for high voltage between the suppl-y and the electron-beam generator.

In accordance with this invention electron-beam weldi' ing apparatus is provided which includes as a primary Patented Dec. 24, 1968 combined as an integrated unit with the electron-beam generator. The supply or converter includes a container having therein the network for converting the voltage received from the fixed generator through the flexible cable to that demanded by the electron-beam generator, which typically is 150,000 volts. The container is lled with a gas of high-dielectric strength usually at the pressure at which the dielectric strength is a maximum. Typical gases providing the high-dielectric strength are sulfur hexatluoride (SP6), peruoropropane ('C3Fa) or octouorocyclobutane (C4F8). Typically, a gas such as sulfur hexailuoride is maintained at an absolute pressure of about 60 pounds per square inch or three atmospheres above atmospheric pressure outside the container. In the interest of portability it is desirable that vthe container be as'light as practicable and to achieve this purpose the -container has cylindrical walls and has spherical end caps.

The voltage-converting network in accordance with this invention includes a step-up transformer which converts the generator voltage to a voltage of intermediate magnitude for example of the order of 38 kilovolts. The network in addition includes a voltage multiplying network composed of an alternating-current capacitorI chain on the input side, a direct-current capacitor lchain on the output iside and a rectifier chain connected in voltage multiplying relationship with the capacitors. To withstand the high voltage to which the components of the network are subjected each chain includes a large number of capacitors or rectiers. Typically the voltage may be quadrupled and in this case there are approximately 52 capacitors each in .the vAC and DC chains and 800 silicon diodes in the rectifier chain.

In accordance with this invention the AC and DC capacitor chains are each mounted in, or formed into, a structure having the general configuration of an open curve which turns back on itself. Specifically, each capacitor chain is mounted in a structure having the form of a generally circular cylinder or ring with a gap having the appearance of a horseshoe. The rectiers also are mounted in, or formed into, a structure having 'the general configuration of an open curve which turns back on itself and in this case also the structure is generally circularly cylindrical with a gap in the periphery.

In accordance with this invention the ring-shaped rectifier and capacitor structures are mounted coaxially with one capacitor structure displaced axially with respect to the other and the rectifier structure within the capacitor structures. The gaps of the capacitor structures are substantially radially outwardly from the gap in the rectifier structure and in corresponding positions in the periphery. That is, the gaps in both the rectifier and the capacitor structures are bounded by substantial common radial planes. The high voltage output terminals of the network are straps forming common junctions respectively between the ends of the DC capacitor structures and adjacent ends of the rectifier structure. There are like straps on the AC side between intermediate points inthe rectier structure and the ends of the AC capacitor structure. The straps on each side are then at the terminal voltages. The positioning of the gaps minimizes the lengths of the straps and the possibility of arc over between a strap and the adjacent portion of a rectifier or capacitor structure. The dielectric strength of the high dielectric strength gas across the -gap suppresses any tendency to arc over between the terminals. The leakage path between the terminals is along the structures and is relatively long.

For a more complete understanding of this invention, both as to its organization and as to its method of operation, together with additional objects and advantages thereof, reference is made to the following description,

3 taken in connection with the accompanying drawings, in which:

FIGURE l is a block diagram of electron-'beam welding apparatus embodying this invention;

FIG. 2 is a `View in elevation of a preferred embodiment of this invention showing the power supply as viewed from below and the electron beam generator with which it forms a unit;

FIG. 3 is a plan view of the supply and generator with a part of the wall of the supply broken away and with certain of the components sectioned;

FIG. 4 is a view in perspective of the capacitor-rectifier unit according to this invention;

FIG. 5 is a view in section taken in the direction along Iline V-V of FIG. 3;

FIG. 6 is a view in section taken along line VI-Vl of FIG. 3;

FIG. 7 is a view in section taken along line VII-VII of FIG. 3;

FIG. 8 is a view partly in section and partly in elevation showing the capacitor ring included in apparatus in accordance with this invention;

FIG. 9 is a view in section taken along line IX-IX of FIG. 8;

FIG. 10 is a. view in section taken along line X--X of FIG. 9;

FIG. ll is a view in elevation of the rectifier ring included in apparatus according to this invention;

FIG. 12 is a view taken along lines XII-XII of FIG. 11; and

FIG. 13 is a schematic of the apparatus according to this invention.

The apparatus shown in the drawings comprises a Low Voltage Generator, -a power supply and an electron beam generator. The electron-beam generator and the supply are combined into an integrated unit. The Low Voltage Generator is connected to this unit through a long, flexible cable 21.

The Low Voltage Generator is capable of supplying power at -a moderate voltage, such as 220 volts, at `a frequency substantially higher than commercial frequency for example 400 cycles. The Power Supply includes a Power Transformer 23 for converting the moderate voltage from the Generator to an intermediate voltage typically 38 kilovolts. The Transformer supplies a High-Voltage net-work 25 which converts the 38 kilovolts to 150,000 volts. The Power Supply also includes a Filament Transformer 27, for supplying the filament 29 of Electron- Beam Generator, and an Auxiliary Supply 31. The Auxiliary Supply is enclosed in a conducting casing 33 which is connected to the hot negative terminal 35 of the High-Voltage Network 25 through a surge resistor 37. The Auxiliary Supply 31 includes a rectifier 39 for rectifying the voltage from the filament transformer 27. Typically the filament is supplied with about 60 amperes at eight volts. The Auxiliary Supply also includes a rectifier 41 for supplying the volt cathode 43 of the Electron Beam Generator. This rectifier 41 is energized from the Low Voltage Generator. The positive terminal of this rectifier is connected to the volt 43 and the negative terminal is connected to a terminal of the filament. Typically the rectifier 41 impresses a voltage of about 150 volts between the volt 43 and the filament 29. The volt 43 is connected -to the grid 45 of the Electron Beam Generator through a resistor 47 which impresses a bias potential on the beam dependent on the current flowing between the volt 43 and the anode 49 of the Beam Generator.

The apparatus shown in the drawings includes a Low Voltage Generator typically operating at a frequency of 400 cycles per second and supplying voltage at about 220 volts and an electron beam Welder. The Power Supply converts the voltage from the Low Voltage Generator into a high voltage typically 150,000 for the electron beam Welder.

The Power Transformer 23, the High-Voltage Network 25, the Auxiliary Supply 31 and the other components 4 of the Power Supply are included in a pressure-tight container 51. To suppress arc-over between high voltage and lower voltage parts of this supply, the container is filled with a high-dielectric-strength gas, such as sulfur hexafluoride, at a pressure of about four atmospheres absolute. So that the container 51 may withstand a pressure, it has a circularly cylindrical wall 53 closed at one end by a spherical end cap or bell 55 and at the other by a partly cylindrical and partly spherical end cap 57 from which a projection 59 extends. The Electron Beam Generator is suspended from the projection 59. The central cylindrical wall 53 of the container 51 has llanges 61 and 63 at each end of the end caps 55 and 57, cooperative with flanges 65 and 67 respectively and the flanges are secured in pairs pressure tight by couplings 69 and 71. To assure pressure tightness gaskets 73 and 75 respectively are in each case interposed in the joint. The couplings 73 and 75 are provided with fastening buckles 77 and 79 which are secured to provide an adequate seal at the joints.

The wall 53 of the container 51 has separate connectors 81 and 83 respectively for the main power conductors 21 and for auxiliary conductors 85 and 87 which supply the volt voltage, the filament transformer 27 and a drive 89 for a heat exchanger 9 1 (FIG. 5). In addition, the wall 53 includes a valve 93 through which the high-dielectric strength :gas is injected into the container 51 and connections and 97 for the cooling of fluid, which is usually water, to the heat exchanger 91. There is in addition a pressure relief valve (not shown).

The projection 59 includes a generally cylindrical tube 101 connected to the end cap 57 at one end and, at the opposite end, to a flanged cylinder 103, whose axis is at right angles to the axis of the container 51. The flange 105 on one side is sealed by an end bell 107 with a gasket 109 interposed to assure pressure tightness. The Electron Beam Generator is suspended pressure tight from the other flange 111. The connection to the Electron Beam Generator is effected through a seal assembly including a generally conical ceramic (porcelain) insulator 113. An outer exible tube is brazed vacuum tight to the top of the insulator 113 and to this tube 115 an inner tube 117 is brazed vacuum tight. The cathode 119, which includes the filament 29 and the bolt 43, is suspended from the tube 117. The conductors 121 for the high voltage, for supplying the filament, for the bolt 43 and for the grid 45 are sealed through a cap 123 brazed to the top of tube 117. The upper end of the ceramic insulator 113 includes the cap 123 and the conductors 121 extend into a tightly closed conducting box 125 which serves as a corona shield. The conductors from the Power Supply for the cathode 119 and the grid 45 extend through a pipe 127 which terminates in the box 125 and in part supports this box. Within the box these conductors are connected to the conductors 121.

The conical insulator 113 carries a flange 129 at its lower end which engages vacuum tight cooperative outer flange 131 of a joint 133 of the Electron Beam Generator. The joint 133 has an outer flange 135 which is sealed to the flange 111 of the tube 103, and also has a projection 137 between flanges 131 and 135. Thefiange 129 on the insulator 113 is sealed vacuum tight by a ring 139 which is screwed into the projection 137. The vacuum chamber 141 of the Electron Beam Generator is thus sealed against the gas in container 51; it is also sealed against penetraltion by the atmosphere.

The Electron Beam Generator includes the anode 49 for accelerating the electrons from the cathode 119 and an array of apertures (not shown) which serve to guide and to an extent concentrate the beam. The Beam Generator also includes focusing coils 142 which provide a concentrated beam. Pump outlets 143 for maintaining the region 141 through which the electron beam passes h1ghly evacuated are provided along the column through which the electron beam passes. The Ibeam is projected out of the column and impinges on work W outside of the evacuated space.

The Power Transformer includes a lprimary, a pair'of secondaries 153 and 155 and a core 157. The core 157 has legs 158 joined near their upper ends by a bar 159. The surfaces 160 of the core 157 of the Power Transformer 23 -are rounded to suppress any tendency towards corona. The secondaries 153 and 155 are suspended from the bar 159. The transformer is suspended from projections 163 extending from the ends of the center wall 53 of the container 51 by plates 165 extending from the legs 158 and secured to these projections. The heat exchanger 91 and its motor 89 are also mounted on the core 157. Tubes 93 are in communication with the heat exchanger 91 in positions to transmit water through its cooling fins (not shown).

The High-Voltage Network 25 includes an AC capacitor chain 171, a DC capacitor chain 173 and a rectifier chain 175. The AC and DC capacitor chains 171 and 173 each have mid-taps 177 and 179 respectively and the rectifiers have a plurality of mid-taps 181, 183, and 185. In FIG. 13 the parts of the chains yinto which the taps divide the chains are shown as separate single capacitors and rectifiers to facilitate understanding of the schematic. Prefer ably each capacitor chain 171 and 173 are divided into a pair of links of substantially equal capacity (26 capacitors typically) by the taps 177 and 179 and the rectifier chain 175 is divided by the taps 181, 183, 185 into four links each having a substantially equal number of diodes (200 typically).

The output terminals 191 and 193 of the secondary 153-155 of the transformer 23 are connected between the intermediate terminal 177 of the AC capacitor chain 171 and the junction of the intermediate terminal 179 of the DC capacitor chain 173 and the central intermediate terminal 183 of the rectifier chain 175. The outer intermediate terminals 181 and 185 of the rectifier Chain 175 are connected to the terminals 195 and 197 of the AC capacitor chain 171 and the end terminals 199 and 201 of the rectifier chain 175 are connected directly to the end terminals 203 and 205 of the DC capacitor chain. Secondary voltage is-quadrupled by this network and is derivable between the junctions of the terminals 203 and 205 and 199 and 201 respectively of the DC capacitors chain and the rectifier chain. One of these terminals 205-201 is grounded. The hot terminal 203-199 is connected to the cathode 119. The anode 49 of the Electron Beam Generator is grounded.

Each capacitor 221 (FIG. of the capacitor chains 171 and 173 consists of alternate layers 223 and 2 25 of a conductor, such as aluminum foil, and an insulator, such as paper, wound into a flattened roll of spiral cross section. The capacitor chains 171 and 173 are each formed into a structure of annular cross section having a gap 227 therein (chain 171 shown in FIGS. 8 and 9). This structure consists of a trough formed between inner and outer rings 229 and 231 of insulating material closed on the bottom by a fiat ring 233 of insulating material. The capacitors 221 are connected in series and disposed in the trough. The trough is then filled with a potting compound 235 preferably a highly insulating epoxy resin. The intermediate terminal 177 extends out of the annular structure and the structure is provided with facilities for effecting a connection.

The rectifiers are silicon diodes 241 which are also mounted in an annular rings having a gap 243. For this purpose the rectifiers are assembled in blocks 245 and the blocks are disposed in a circular form (not shown) having a gap. The rectifiers 241 in each block 245 are connected in series and the blocks are so disposed that adjacent blocks conduct in opposite directions. The adjacent blocks are interconnected so that all of the rectifiers form a series chain. The form is then filled with an epoxy resin 249 which after becoming solidified constitutes an annular structure having the gap 243 on one side and having terminals 203 and 205 at the ends and intermediate terminals 181, 183, 1-85 to provide the connections shown 6 in FIG. 13. The rectifier ring is of substantially smaller diameter than the capacitor rings 171 and 173. The ring in which the rectifiers 241 are mounted has molded projecting lips 251 which serve for securing the parts by means of which the rectifier ring is suspended in the container 51.

The capacitor chains or rings 171 and 173 are of greater diameter than the rectifier chain 175. The capacitor chains 171 and 173 are mounted coaxially, displaced axially and the rectifier chain 175 is mounted within the capacitor chains, with the gaps 227 of the capacitor chains extending radially lfrom the gap 243 of the rectifier chain.

The rectifier chain or ring 175 carries a pair of r'cross insulators 261 and 263 isecured to the opposite lips 251 by studs 264. The AC capacitor ring 171 is suspended from the cross insulator 261 on one side by a pair of insulating strips A265 and 267 secured to the capacitor chain 171 and also to the cross insulator 261. The v DC capacitor chain 173 is similarly suspended from the re'ctifier chain 175 by strips 266 and 268. The cross strip 261 from which the AC capacitor chain 171 is suspended carries at its ends insulating strips 269 and 271 :from which a plurality of sets of' internally threaded bars. 275 land 277 extend. These bars 275 and 277 are screwed to the fianges 61 extending on the adjacent side from the central portion 53 of the container 51. The bars 275 and 277 engage angle brackets 279 and 281 secured to the transformer core 157 and serve as additional support for the transformer -core 157. On the opposite side the cross insulator 263 is secured to angle brackets 281 and 293 which are in turn secured to the adjacent ange of the center portion 53 of the container 51.

Connecting straps are provided to effect the connections sh-own in FIG. 13. A pair of straps 291 and 293 extend between the ends at the gap of the AC capacitor ring 171 and intermediate taps 181 and 185 of the rectifier ring 175. Another strap 295 extends from the center tap of the rectifier ring 175 and is connected to one terminal 191 of the secondary 155 of the power transformer 23. A further strap 297 extends from the center tap 177 of the AC capacitor ring 171, and is connected to the other terminal 193 of the secondary. The straps 291, 293, 295, 297 are securely bolted and connected to the capacitor and tothe rectifier rings at each point. Straps 301 and 303 arel also connected between'the ends at the gap 227 of the DC capacitor ring 173 and the ends at the gap 243 of the rectifier ring 175. A strap 305 is also connected between the center tap 179 of the DC capacitor ring 173 and the center tap 183 of the rectifier ring Within the container 51 there is also the filament transformer 27 suspended from a bracket 311 connected to the end cap 57 from which the projection 59 extends. The -auxiliary power supply 31 is suspended from another bracket. The bleeder resistor 37 is on a bracket. Conductors 121 lfor energizing the Electron-Beam Generator pass through the pipe 127 and the projection 59 extending from the end cap 57 and are connected to the appropriate terminals of the Generator from which the cathode grid assembly 29-43-45 is suspended.

In the use of the apparatus the power supply is mounted in the container 51 and connected as shown and the container is evacuated and filled with the high-dielectricstrength gas. The control and output terminals of the power supply are also connected to the cathode- 29-45 of the Electron-Beam Generator as shown. IIn the use of the apparatus the Beam Generator and power supply may be moved readily over a wide area and welding performed on the work W in the positions where the work is located.

In the practice of this invention a Power Supply is provided which operates satisfactorily to energize an Electron Beam Generator of electron-beam welding apparatus. This supply has the following characteristics:

Output voltage-150 kilovolts DC supplied with the nega- Input` voltage-220 volts AC, 400 cycles per second.

tive pole hot and the positive pole grounded. Maximum current-80 `milliamperes.

The components of the supply including the Power Transformer, the High-Voltage Network and the Auxiliary Supply are mounted in a sealed container 51 filled with sulfur hexauoride at 60 pounds per square inch absolute pressure (45 lbs. above atmospheric). The container 51 within which the supply is enclosed has a diameter of l inches and is 28 inches long. The total weight of this supply is 150 pounds. The High-Voltage Network in this supply has as overall dimensions, a diameter of 12 inches and a length of 61/2 inches.

As shown in FIG. 13 the High-Voltage Network escalates the voltage over a wide range from capacitor 221 to capacitor 221 and rectifier bank 245 to rectifier bank 245 and a long continuous circuit path is necessary. To span a 61/2 inch dimension with components between which there is a potential difference of 150 kv. would impress an excessive voltage gradient for surface creepage in apparatus in accordance with the prior art. The ringshaped rectifier and capacitor structures 175, 171, 173 maintains the gradient throughout within safe limits. This structure also has the advantage that it dovetails into the cylindrical shape of the container 51 needed for pressure resistance. The circumferences of the structures avail adequate creepage path. The ring shape also is superior with respect to voltage gradients between components and ybetween components and ground planes. For instance, the capacitors 221 in the chains are concentric within the surrounding wall 53 of the cylindrical pressure vessel. The rectifiers 24 are also concentric and lie within the capacitors 221 and this affords the superior gradients.

The elements in the rectifier-ring structure 175 are silicon diodes encapsulated in epoxy in a configuration to eliminate sharp edges and minimize corona. The rectifier ring structure 17S in the typical supply described above is 6.50 inches long and has a diameter of 6.00 inches and a gap 1.5 inches wide. The capacitor rings 171 and 173 have inside diameters of 91A inches andoutside diameters of l2 inches and a thickness of about 3% inches. They are spaced so that the rectifier ring 175 is wholly within the capacitor ring 171 and 173 with an annular gas space of 1% inches between the rectifier and capacitor rings. The gaps 227 andA 243 andthe spaces are adequate for insulation purposes. The assembly is mounted in the con- V tainer 51 by means of strips 261, 263, 26S, 267, 269, 271, 275, 277 of glass mica insulation.

The capacitor rings 171 and 173 consist of numerous small tubular capacitors 221 each pressed in an oval shape (FIG. The individual elements are series connected positioned in an epoxy cake mol shell and then encapsulated in epoxy.

While preferred embodiments of this invention have been disclosed herein many modifications thereof are feasible. This invention then is not to be restricted except insofar as is necessitated by the spirit of the prior art.

We claim as our invention:

1. A high-voltage power supply for a portable electronbeam work-treating apparatus comprising a container having therein a plurality of rectiers connected in series, a plurality of capacitors connected in series, input terminals for supplying potential, means connecting said terminals, said rectifiers and said capacitors in a voltagerectifying network having output terminals between which said high voltage is derivable, the said supply being characterized by the fact that said rectifiers and said capacitors are each individually mounted in an individual structure having a cross section having the general configuration of an open curve which turns back on itself so that its ends are adjacent, the output terminals being near opposite points of said gap, and a high dielectric strength insulating medium bridging the gap to provide a highly insulating medium between said high voltage terminals.

2. The supply of yclaim 1 wherein the rectifier structure is mounted within the capacitor structure.

3. The supply of claim 2 wherein each structure has the form of a circular cylinder having a gap in its periphery, the cylinders being mounted coaxially with the rectifier cylinder located within the capacitor cylinders, and the gap in the capacitor cylinder extending generally radially from the gap in the rectifier cylinder.

4. The supply of claim 3 wherein the container is of generally cylindrical form generally coaxial with the rectifier and capacitor structures and the high dielectric medium is a high-dielectric-strength gas at an elevated pressure.

5. The supply of claim 1 including a step-up transformer within the container having a low voltage primary and substantially higher voltage secondary, the input terminals being connected in voltage transfer relaitonship with said secondary.

6. The supply of claim 5 wherein the higher output voltage of the secondary is of magnitude intermediate the low voltage of the primary and the high voltage of the supply, and the rectifiers and capacitors are connected in a voltage-multiplying network.

7. The supply of claim 6 wherein the container is of generally circular cylindrical form and the rectifier and capacitor structures are of generally circular cylindrical form generally coaxial with the container with the rectifier structure within the capacitor structure.

8. A high-voltage direct current supply comprising an alternating current capacitor structure including a plurality of capacitors connected in series and mounted in a generally circular cylindrical configuration having a gap therein, a direct-current capacitor structure including a plurality of capacitors connected in series and mounted in a generally circular cylindrical configuration having a gap therein generally coaxial with the alternating-current capacitor structure and axially displaced from said alternating current structure, a rectifier structure including a plurality of rectifiers mounted in a circular cylindrical configuration having a gap therein generally coaxial with said capacitor structures and within said capacitor structures, the gaps in said capacitor structures being bound by substantially the same radial planes, alternating-current terminals, and means connecting said capacitors, rectifiers and terminals in a voltage-multiplier network.

References Cited UNITED STATES PATENTS 2,619,602 1l/1952 Walker et al 307-110 2,875,394 2/1959 Cleland 307-110 X 3,048,766 8/1962 Panzer 307-110 X 3,218,431 11/1965 Stauffer 219-121 JAMES W. LAWRENCE, Primary Examiner'.

R. L. JUDD, Assistant Examiner.

U.S. C1.X.R. 

